The present invention relates to a method and system for measuring the temperature of an environment, such as the interior of the body.
In many circumstances it is important to measure the temperature inside a material body. Such circumstances may occur during industrial processes or exploration and analysis processes, such as in geophysical probing or in medical diagnostics and treatment of internal parts of the body.
Conventional thermometry and absolute thermometry are known methods for measuring temperature.
Conventional thermometry is based upon the temperature coefficient of properties of materials, such as resistance or mechanical expansion.
Absolute thermometry is a method which directly measures thermal energy of a sensor resistance. This method is based upon the known physical phenomenon of spontaneous thermal noise arising from the Brownian motion of ionized molecules within a resistance.
Thermal noise, which can be discussed in terms of thermal current, provides a direct measurement of temperature on a thermodynamic scale, thus the Boltzmann constant defines the temperature. The phenomenon of thermal noise is derived, for example, in the book: CCD arrays cameras and displays by Hoist G. C., p. 128, 2nd edition, SPIE Press, 1998. The formula used to define thermal current is:
 less than in2 greater than =kTC
where k is the Boltzmann constant, T is the temperature of a sensor, and C is the capacitance of the sensor. Thus the magnitude of the signals produced by the thermal current is directly proportional to the square root of the temperature of the sensor. Experiments have indicated that the signal doubles with the increase of 7xc2x0 C. (degrees Centigrade), which means that a resolution better than 0.1xc2x0 C. is achieved.
In image sensors, the thermal current produced in an operating photodetector device, when no optical radiation impinges on the detector, is called xe2x80x9cdark currentxe2x80x9d. In CCD cameras dark current is basically charge which accumulates in the CCD pixels due to thermal noise. The effect of dark current is to produce an additive quantity to the electron count in each pixel.
U.S. Pat. No. 3,937,086 to von Thuna, U.S. Pat. No. 5,354,130 to Seppa et al. and U.S. Pat. No. 5,098,197 to Shepard et al. all describe devices for measuring the absolute temperature of a body material by receiving and analyzing the thermal noise of the body material.
U.S. Pat. No. 4,246,784 to Bowen describes a method for noninvasive temperature measurement of the interior of a body using the acoustic thermal noise spectrum of the measured body.
None of these temperature measurement methods utilize an image sensor to measure the thermal noise of a body material.
The present invention provides a method and system for sensing the temperature of an environment, such as inside a body, by calculating the temperature of an image sensor in the environment and deducing the environment""s temperature from the image sensor""s calculated temperature. The temperature of the image sensor is calculated by measuring its generated dark current noise.
The method and system of the present invention have the advantage of utilizing an image sensor, in which thermal noise is easily detectable, for deducing the temperature of a material body. Furthermore, according to the invention, a single sensor is utilized for obtaining visual data and data relating to the temperature of the environment. Thus, diverse information about an environment can be obtained utilizing a single sensing device.
There is thus provided according to the present invention a method for sensing the temperature of an environment comprising the steps of introducing into an environment an image sensor having an image sensing module, sensing the dark current noise of the image sensor, calculating the temperature of the image sensor, calculating the temperature of the environment and optionally displaying the calculated environment temperature.
It will be appreciated that the term xe2x80x9cenvironmentxe2x80x9d in the present invention relates to a space enclosed within walls in which it is desired to measure the temperature of the space and/or of the walls.
The temperature of the image sensor is indicative of the temperature of it""s immediate surroundings and, relying on known factors such as heat distribution, distance from the image sensor, etc., the temperature of further areas can also be calculated.
The image sensors utilized in the invention can be digital cameras or video cameras such as vidiocon, CCD cameras or CMOS cameras.
The present invention further provides a system for sensing the temperature of an environment. The system comprises an image sensor having an image sensing module in communication with an integrating unit for detecting the dark current of the image sensor image sensing module and for calculating the temperature of the image sensor. The integrating unit may further calculate the temperature of the environment or the temperature of the environment may be calculated, based on data from the integrating unit, by a separate unit that is in communication with the integrating unit
The integrating unit may have an amplifying function for amplifying signals received from the image sensor.
The communication between the image sensor and integrating unit can be optionally controlled according to the illumination conditions, optionally through a switch which enables communication only during periods in which the sensor is not illuminated.